Matthew Forbes - Academia.edu (original) (raw)

Papers by Matthew Forbes

Rapid communications in mass spectrometry : RCM, Jan 30, 2014

RATIONALE: In recent years, research and applications of the N 2 O site-specific nitrogen isotope... more RATIONALE: In recent years, research and applications of the N 2 O site-specific nitrogen isotope composition have advanced, reflecting awareness of the contribution of N 2 O to the anthropogenic greenhouse effect, and leading to significant progress in instrument development. Further dissemination of N 2 O isotopomer analysis, however, is hampered by a lack of internationally agreed gaseous N 2 O reference materials and an uncertain compatibility of different laboratories and analytical techniques. METHODS: In a first comparison approach, eleven laboratories were each provided with N 2 O at tropospheric mole fractions (target gas T) and two reference gases (REF1 and REF2). The laboratories analysed all gases, applying their specific analytical routines. Compatibility of laboratories was assessed based on N 2 O isotopocule data for T, REF1 and REF2. Results for T were then standardised using REF1 and REF2 to evaluate the potential of N 2 O reference materials for improving compatibility between laboratories. RESULTS: Compatibility between laboratories depended on the analytical technique: isotope ratio mass spectrometry (IRMS) results showed better compatibility for δ 15 N values, while the performance of laser spectroscopy was superior with respect to N 2 O site preference. This comparison, however, is restricted by the small number of participating laboratories applying laser spectroscopy. Offset and two-point calibration correction of the N 2 O isotopomer data significantly improved the consistency of position-dependent nitrogen isotope data while the effect on δ 15 N values was only minor. CONCLUSIONS: The study reveals that for future research on N 2 O isotopocules, standardisation against N 2 O reference material is essential to improve interlaboratory compatibility. For atmospheric monitoring activities, we suggest N 2 O in whole air as a unifying scale anchor.

... CONCLUSION The 14C dates presented in this paper give an approximate age of the bulk SOM cont... more ... CONCLUSION The 14C dates presented in this paper give an approximate age of the bulk SOM contained within the organic-rich layer of the Black Creek Swamp excavation site at Rocky River, Kangaroo Island. The dates ...

Rapid Communications in Mass Spectrometry, 2014

RATIONALE: In recent years, research and applications of the N 2 O site-specific nitrogen isotope... more RATIONALE: In recent years, research and applications of the N 2 O site-specific nitrogen isotope composition have advanced, reflecting awareness of the contribution of N 2 O to the anthropogenic greenhouse effect, and leading to significant progress in instrument development. Further dissemination of N 2 O isotopomer analysis, however, is hampered by a lack of internationally agreed gaseous N 2 O reference materials and an uncertain compatibility of different laboratories and analytical techniques. METHODS: In a first comparison approach, eleven laboratories were each provided with N 2 O at tropospheric mole fractions (target gas T) and two reference gases (REF1 and REF2). The laboratories analysed all gases, applying their specific analytical routines. Compatibility of laboratories was assessed based on N 2 O isotopocule data for T, REF1 and REF2. Results for T were then standardised using REF1 and REF2 to evaluate the potential of N 2 O reference materials for improving compatibility between laboratories. RESULTS: Compatibility between laboratories depended on the analytical technique: isotope ratio mass spectrometry (IRMS) results showed better compatibility for δ 15 N values, while the performance of laser spectroscopy was superior with respect to N 2 O site preference. This comparison, however, is restricted by the small number of participating laboratories applying laser spectroscopy. Offset and two-point calibration correction of the N 2 O isotopomer data significantly improved the consistency of position-dependent nitrogen isotope data while the effect on δ 15 N values was only minor. CONCLUSIONS: The study reveals that for future research on N 2 O isotopocules, standardisation against N 2 O reference material is essential to improve interlaboratory compatibility. For atmospheric monitoring activities, we suggest N 2 O in whole air as a unifying scale anchor.

Hydrogeology Journal, 2012

The Drummond Nature Reserve (DNR), a highvalue conservation area 100km northeast of Perth, Wester... more The Drummond Nature Reserve (DNR), a highvalue conservation area 100km northeast of Perth, Western Australia, contains two rare freshwater claypans and a diverse range of rare and threatened vascular plants. Groundwater/surface-water interactions were investigated via isotopic (δ 18 O and δD) and major ion analysis. The groundwater chemical and isotope analyses combined with nutrient data allowed for the assessment of potential hydrologically derived threats to the claypans and their associated conservation values. Groundwater composition is typically Na-Cl to Na-Mg-Cl; whereas the claypan's ephemeral fresh surface water is Na-Cl-HCO 3 . Distinct δ 18 O and δD isotopic signatures for the claypan surface waters and adjoining groundwaters indicate that there currently is minimal connection between these two hydrological systems. Hence the current threat to the freshwater claypans and associated biota from rising saline and acidic groundwater is minimal. Elevated nutrient (N) levels identified in groundwaters along the reserve's western boundary may be linked to fertiliser regimes employed in adjoining agricultural lands. The ecosystem associated with the southwest claypan is particularly vulnerable to N and P inputs via surface-water flows, which could cause algal blooms, vegetation degradation and weed infestation.

Geomorphology, 2007

The origin of the sediments located in the Naracoorte Caves (South Australia) was investigated vi... more The origin of the sediments located in the Naracoorte Caves (South Australia) was investigated via the analysis of strontium isotope ratios (87Sr/86Sr), elemental geochemistry, and mineralogy. Sedimentary deposits located in Robertson, Wet, Blanche and several other chambers in Victoria Cave are all variable mixes of fine sand and coarse silts, which display similar and consistent strontium isotope ratios (0.717–0.725). This suggests that over the 400 ka time frame that these deposits span there has been minimal variation in the source of the clastic sediments. Increased strontium concentrations for these cave sediments correspond with increasing silt content, yet there is no correlation between 87Sr/86Sr ratios and silt content. This implies that the silt-sized component of the sediments is the main contributor of strontium to the cave sediments. Comparisons of 87Sr/86Sr with regional surficial deposits show a significant correlation between the cave sediments (avg: 0.7228; n = 27), the fine silt lunettes of the Bool Lagoon area (avg: 0.7224; n = 4), the sandy A horizons of the Coonawarra Red Brown Earths (RBEs; avg: 0.726; n = 5), and Holocene age podsolic sand deposits (0.723). These data suggest that there has been substantial flux from this group of deposits to the caves, as would be expected considering prevailing winds. This relationship is further supported by a strong correlation between many trace elements, including Ti, Zr, Ce, and Y; however, variations in clay mineralogy suggest that the fine silt-dominated lunettes and Padthaway RBEs were not significant contributors to the cave deposits. Hence, the detritus entering the caves was more than likely from areas proximal to the cave entrance and was dominated by medium grain-sized materials. Major regional deposits, including the coarser-grained, calcite-rich Bridgewater Formation sands, basalts from the lower SE, Padthaway Horst granites, Gambier limestone, and metamorphics from the Adelaide geosyncline show minimal correlation in 87Sr/86Sr ratios, elemental geochemistry, and mineralogy with the cave sediments, and are discounted as significant sources. In comparison, 87Sr/86Sr ratios for the Coorong silty sands (0.717–0.724), Lower Murray sands (0.727–0.730), and the medium size silt component of the Murray–Darling River system (0.71–0.72), compare favourably with the cave sediments. This relationship is further supported by similarities in elemental chemistry and mineralogy. Thus, much of the strontium-rich silt that is now located in the Naracoorte Cave sediments likely originated from the Murray–Darling basin. Over time, this material has been transported to the SE of South Australia, where it mixed with the medium sand component of the regressive dune ridge sequence, locally derived organic matter, limestone fragments, and fossil material to produce the unique deposits that we see evident in many of the chambers of the Naracoorte Cave system today.

Sedimentary Geology, 2010

Located in the south-west coastal zone of Western Australia are numerous tufa deposits, which are... more Located in the south-west coastal zone of Western Australia are numerous tufa deposits, which are registered as Threatened Ecological Communities (TEC). The tufas occur in near-shore shallow bedrock settings and are associated with local groundwater discharge. Depositional facies, mineralogy, elemental chemistry and water quality were investigated for five key deposits. Two conceptual environmental models are identified. The first, the cascade to barrage pool model is associated with coastal waterfall zones, the second, a perched spring-line and barrage pool model is located predominantly in the supratidal zone. Tufa morphology, texture, mineral composition and elemental chemistry vary within and between sites. Both phytoclast and lithoclast (allochthonous), and phytoherm forms of tufa are identified depending on location within the facies. Calcite, and to a lesser extent, aragonite and Mg-calcite dominate tufa mineralogy, with diagenetic modifications apparent. Tufa water chemistry is generally Na-Cl-HCO 3 dominated; however, Na-Cl concentrations increase at sites situated within the supratidal zone. Currently the most likely potential threat posed to these deposits is increasing nutrient levels in spring waters from agricultural land use within the catchments. This could in the future impact on tufa development.

Rapid communications in mass spectrometry : RCM, Jan 30, 2014

RATIONALE: In recent years, research and applications of the N 2 O site-specific nitrogen isotope... more RATIONALE: In recent years, research and applications of the N 2 O site-specific nitrogen isotope composition have advanced, reflecting awareness of the contribution of N 2 O to the anthropogenic greenhouse effect, and leading to significant progress in instrument development. Further dissemination of N 2 O isotopomer analysis, however, is hampered by a lack of internationally agreed gaseous N 2 O reference materials and an uncertain compatibility of different laboratories and analytical techniques. METHODS: In a first comparison approach, eleven laboratories were each provided with N 2 O at tropospheric mole fractions (target gas T) and two reference gases (REF1 and REF2). The laboratories analysed all gases, applying their specific analytical routines. Compatibility of laboratories was assessed based on N 2 O isotopocule data for T, REF1 and REF2. Results for T were then standardised using REF1 and REF2 to evaluate the potential of N 2 O reference materials for improving compatibility between laboratories. RESULTS: Compatibility between laboratories depended on the analytical technique: isotope ratio mass spectrometry (IRMS) results showed better compatibility for δ 15 N values, while the performance of laser spectroscopy was superior with respect to N 2 O site preference. This comparison, however, is restricted by the small number of participating laboratories applying laser spectroscopy. Offset and two-point calibration correction of the N 2 O isotopomer data significantly improved the consistency of position-dependent nitrogen isotope data while the effect on δ 15 N values was only minor. CONCLUSIONS: The study reveals that for future research on N 2 O isotopocules, standardisation against N 2 O reference material is essential to improve interlaboratory compatibility. For atmospheric monitoring activities, we suggest N 2 O in whole air as a unifying scale anchor.

... CONCLUSION The 14C dates presented in this paper give an approximate age of the bulk SOM cont... more ... CONCLUSION The 14C dates presented in this paper give an approximate age of the bulk SOM contained within the organic-rich layer of the Black Creek Swamp excavation site at Rocky River, Kangaroo Island. The dates ...

Rapid Communications in Mass Spectrometry, 2014

RATIONALE: In recent years, research and applications of the N 2 O site-specific nitrogen isotope... more RATIONALE: In recent years, research and applications of the N 2 O site-specific nitrogen isotope composition have advanced, reflecting awareness of the contribution of N 2 O to the anthropogenic greenhouse effect, and leading to significant progress in instrument development. Further dissemination of N 2 O isotopomer analysis, however, is hampered by a lack of internationally agreed gaseous N 2 O reference materials and an uncertain compatibility of different laboratories and analytical techniques. METHODS: In a first comparison approach, eleven laboratories were each provided with N 2 O at tropospheric mole fractions (target gas T) and two reference gases (REF1 and REF2). The laboratories analysed all gases, applying their specific analytical routines. Compatibility of laboratories was assessed based on N 2 O isotopocule data for T, REF1 and REF2. Results for T were then standardised using REF1 and REF2 to evaluate the potential of N 2 O reference materials for improving compatibility between laboratories. RESULTS: Compatibility between laboratories depended on the analytical technique: isotope ratio mass spectrometry (IRMS) results showed better compatibility for δ 15 N values, while the performance of laser spectroscopy was superior with respect to N 2 O site preference. This comparison, however, is restricted by the small number of participating laboratories applying laser spectroscopy. Offset and two-point calibration correction of the N 2 O isotopomer data significantly improved the consistency of position-dependent nitrogen isotope data while the effect on δ 15 N values was only minor. CONCLUSIONS: The study reveals that for future research on N 2 O isotopocules, standardisation against N 2 O reference material is essential to improve interlaboratory compatibility. For atmospheric monitoring activities, we suggest N 2 O in whole air as a unifying scale anchor.

Hydrogeology Journal, 2012

The Drummond Nature Reserve (DNR), a highvalue conservation area 100km northeast of Perth, Wester... more The Drummond Nature Reserve (DNR), a highvalue conservation area 100km northeast of Perth, Western Australia, contains two rare freshwater claypans and a diverse range of rare and threatened vascular plants. Groundwater/surface-water interactions were investigated via isotopic (δ 18 O and δD) and major ion analysis. The groundwater chemical and isotope analyses combined with nutrient data allowed for the assessment of potential hydrologically derived threats to the claypans and their associated conservation values. Groundwater composition is typically Na-Cl to Na-Mg-Cl; whereas the claypan's ephemeral fresh surface water is Na-Cl-HCO 3 . Distinct δ 18 O and δD isotopic signatures for the claypan surface waters and adjoining groundwaters indicate that there currently is minimal connection between these two hydrological systems. Hence the current threat to the freshwater claypans and associated biota from rising saline and acidic groundwater is minimal. Elevated nutrient (N) levels identified in groundwaters along the reserve's western boundary may be linked to fertiliser regimes employed in adjoining agricultural lands. The ecosystem associated with the southwest claypan is particularly vulnerable to N and P inputs via surface-water flows, which could cause algal blooms, vegetation degradation and weed infestation.

Geomorphology, 2007

The origin of the sediments located in the Naracoorte Caves (South Australia) was investigated vi... more The origin of the sediments located in the Naracoorte Caves (South Australia) was investigated via the analysis of strontium isotope ratios (87Sr/86Sr), elemental geochemistry, and mineralogy. Sedimentary deposits located in Robertson, Wet, Blanche and several other chambers in Victoria Cave are all variable mixes of fine sand and coarse silts, which display similar and consistent strontium isotope ratios (0.717–0.725). This suggests that over the 400 ka time frame that these deposits span there has been minimal variation in the source of the clastic sediments. Increased strontium concentrations for these cave sediments correspond with increasing silt content, yet there is no correlation between 87Sr/86Sr ratios and silt content. This implies that the silt-sized component of the sediments is the main contributor of strontium to the cave sediments. Comparisons of 87Sr/86Sr with regional surficial deposits show a significant correlation between the cave sediments (avg: 0.7228; n = 27), the fine silt lunettes of the Bool Lagoon area (avg: 0.7224; n = 4), the sandy A horizons of the Coonawarra Red Brown Earths (RBEs; avg: 0.726; n = 5), and Holocene age podsolic sand deposits (0.723). These data suggest that there has been substantial flux from this group of deposits to the caves, as would be expected considering prevailing winds. This relationship is further supported by a strong correlation between many trace elements, including Ti, Zr, Ce, and Y; however, variations in clay mineralogy suggest that the fine silt-dominated lunettes and Padthaway RBEs were not significant contributors to the cave deposits. Hence, the detritus entering the caves was more than likely from areas proximal to the cave entrance and was dominated by medium grain-sized materials. Major regional deposits, including the coarser-grained, calcite-rich Bridgewater Formation sands, basalts from the lower SE, Padthaway Horst granites, Gambier limestone, and metamorphics from the Adelaide geosyncline show minimal correlation in 87Sr/86Sr ratios, elemental geochemistry, and mineralogy with the cave sediments, and are discounted as significant sources. In comparison, 87Sr/86Sr ratios for the Coorong silty sands (0.717–0.724), Lower Murray sands (0.727–0.730), and the medium size silt component of the Murray–Darling River system (0.71–0.72), compare favourably with the cave sediments. This relationship is further supported by similarities in elemental chemistry and mineralogy. Thus, much of the strontium-rich silt that is now located in the Naracoorte Cave sediments likely originated from the Murray–Darling basin. Over time, this material has been transported to the SE of South Australia, where it mixed with the medium sand component of the regressive dune ridge sequence, locally derived organic matter, limestone fragments, and fossil material to produce the unique deposits that we see evident in many of the chambers of the Naracoorte Cave system today.

Sedimentary Geology, 2010

Located in the south-west coastal zone of Western Australia are numerous tufa deposits, which are... more Located in the south-west coastal zone of Western Australia are numerous tufa deposits, which are registered as Threatened Ecological Communities (TEC). The tufas occur in near-shore shallow bedrock settings and are associated with local groundwater discharge. Depositional facies, mineralogy, elemental chemistry and water quality were investigated for five key deposits. Two conceptual environmental models are identified. The first, the cascade to barrage pool model is associated with coastal waterfall zones, the second, a perched spring-line and barrage pool model is located predominantly in the supratidal zone. Tufa morphology, texture, mineral composition and elemental chemistry vary within and between sites. Both phytoclast and lithoclast (allochthonous), and phytoherm forms of tufa are identified depending on location within the facies. Calcite, and to a lesser extent, aragonite and Mg-calcite dominate tufa mineralogy, with diagenetic modifications apparent. Tufa water chemistry is generally Na-Cl-HCO 3 dominated; however, Na-Cl concentrations increase at sites situated within the supratidal zone. Currently the most likely potential threat posed to these deposits is increasing nutrient levels in spring waters from agricultural land use within the catchments. This could in the future impact on tufa development.